The present invention concerns the testing of integrated circuits and pertains particularly to the versatile testing of function systems blocks within a complex device.
Function system blocks implement a sub-function within the larger function of a complex device. The functionality of a function system block is difficult to test when contained within a larger body of logic.
Typically, the function system blocks are tested using a special test mode that externalizes the internal function system block to be tested by a method that maps the internal input/output connection of the function system block to the input/output pins of the larger device. This is accomplished, for example, by multiplexing each internal block connection to an external pin. Alternatively, the internal input/output connection of the function system block may be mapped to the input/output pins of the larger device by using serial boundary scan techniques that allow access to the internal connections through a few external pins. However, these methods often increase the die area of the device, degrade signal timing, increase internal interconnection complexity and/or increase the test program time.